Field of the Invention
The present invention relates to a manufacturing method of the pneumatic tire which can discharge a static electricity generated in a vehicle body and a tire to a road surface.
Description of the Related Art
Recently, there have been proposed a pneumatic tire including a tread rubber blended with silica at a high ratio in order to reduce the rolling resistance that largely affects the fuel consumption of a vehicle and to increase braking performance (WET braking performance) on a wet road surface. However, compared to a tread rubber blended with carbon black at a high ratio, the electric resistance of such tread rubber is high, and accordingly, static electricity generated on a vehicle body or the tire is prevented from being released to the road surface. As a result, problems like radio noises tend to occur.
Accordingly, there has been developed a pneumatic tire which can achieve electrical conduction performance by forming a conductive portion made of a conductive rubber blended with carbon black or the like, in a tread rubber made of a nonconductive rubber blended with silica or the like. For example, in a pneumatic tire described in Patent Document 1, a tread rubber which is formed by a nonconductive rubber is provided with a conductive portion in which one end is exposed to a ground-contacting surface and the other end is connected to a side wall rubber or a topping rubber of a carcass.
However, in the tread rubber which is provided in the pneumatic tire mentioned above, since a conductive portion which is continuously provided in a tire circumferential direction and is formed as an L-shaped cross section is expanded like a uniform sheet, and a much volume of conductive rubber is included, it has been known that an improvement of a performance can be expected by reducing it. In addition, in practice, it is important to enhance a forming efficiency of the tread rubber so as to improve a productivity.